Climate control blows cold until restarting engine

[JB Mitchell]

My 2003 Toyota 100 will not blow heat (at any climate control setting) when first started and driven for any distance or time. Whether it is 10 minutes or 2 hours. If you turn off the ignition though, and restart the engine once the engine has warmed up, it will immediately begin to produce heat. From that point on the heat will continue to work until the engine has cooled down. (You are able to turn off and restart many times with no problem as long as the engine stays warm.) Then when the engine is cold, the problem repeats itself with no heat until you go through the restart process again.

 

[Mike6158]

My 2003 Toyota 100 will not blow heat (at any climate control setting) when first started and driven for any distance or time. Whether it is 10 minutes or 2 hours. If you turn off the ignition though, and restart the engine once the engine has warmed up, it will immediately begin to produce heat. From that point on the heat will continue to work until the engine has cooled down. (You are able to turn off and restart many times with no problem as long as the engine stays warm.) Then when the engine is cold, the problem repeats itself with no heat until you go through the restart process again.

Engine coolant supplies the heat to the heating coil(s) in the climate control unit. If the engine isn't warm neither is the coolant.

 

[JB Mitchell]

Thanks Mike! I should have mentioned that I have checked the cooling system and the the engine coolant is full and the radiator and temperature gauge are heating up normally.

 

[Mike6158]

And I should have read the first sentence with more attention

My 2003 Toyota 100 will not blow heat (at any climate control setting) when first started and driven for any distance or time.

My 2000 did just the opposite yesterday. The front AC unit would not come on. After a little bit of "knob twiddling" it finally came and behaved normally for the rest of the day.

I've also noticed that the heater blower wasn't working for a bit and then suddenly came on full blast eventually settling down to a normal level and working. I think there must be a sensor in the system that hangs up from time to time. Maybe someone that knows more about TLC electrical will chime in

 

[re_guderian]

What's your engine temp? Could be thermostat stuck/sticking. I finally had to replace a thermostat the other day in my 2000 due to intermittent no heat in the AM's. I would think, though, that after two hours, tire engine should be running hot. What are ambient temps? Good news is that t-stat is a third of a banana job...

 

[Julian Stead]

The heater coil should get heat without the thermostat opening. I would see if there is any air in coolant system, put your hands on the pipes attaching to the heater coil to see if there hot when it is blowing cold air. Air does get trapped in the heater coil. Just run the vehicle from cold with the radiator cap off until the thermostat opens, top up if required. Recheck level over the next few days when cold. Could even be a faulty heater flap in the heater box.

 

[re_guderian]

The heater coil should get heat without the thermostat opening. I would see if there is any air in coolant system, put your hands on the pipes attaching to the heater coil to see if there hot when it is blowing cold air. Air does get trapped in the heater coil. Just run the vehicle from cold with the radiator cap off until the thermostat opens, top up if required. Recheck level over the next few days when cold. Could even be a faulty heater flap in the heater box.

In my experience, the jiggle valve wasn't enough to provide heat in the cabin.

 

[Julian Stead]

The jiggler valve doesn't feed the heater, the heater coil gets water circulated from the engine before the thermostat so the thermostat has no effect on the heater. The thermostat just controls engine temp by allowing water into the radiator to cool when required.